In the design of data connectors, the problems of signal cross talk and signal integrity are always at issue. For data connectors used with high speed data rates, in excess of 1.0 gigabit/second, the cross talk and signal integrity problems may be more pronounced.
A problem with current state of the art high speed serial data connectors is two-fold. First, current connector designs used with high speed serial data transmission lines require the transition of industry standard cable wire geometry to an industry standard circuit board attachment geometry. The current primary industry standard cable wire is quad cable. This type of cable is configured as four separate wires twisted around a common center with the two signal lines of a pair being diametrically opposed to each other. In other words, the cross-sectional view of a quad cable would have four wires at the four corners of a square such that the two signal lines of a differential pair are located at the respective opposite corners of the square.
The industry standard geometry for attachment of the conductors to the circuit board is four wires in line and adjacent to each other. The two signal lines of a pair are directly adjacent to each other and are positioned as far from the other pair of signal lines as is possible to reduce potential signal cross talk. As an additional means to reduce cross talk, the two signal line pairs are often separated by a ground line.
The transition in geometry of the signal wires from a twisted quad arrangement to an in-line arrangement requires that one of the signal lines of one of the pairs cross through the signal lines of the other pair. The state of the art of data connectors and the prior art theory provides that crossing one signal line through another pair of signal lines results in unacceptably high levels of cross talk. In view of this belief, current connector designs accomplish the crossing of signal lines in the printed circuit board within the connector.
The cross over of the signal lines in the circuit board is generally achieved by incorporating extra plated through holes or traces for each wire of the signal cable pair. To accomplish the signal line cross over, certain plated through holes will necessarily be unmatched or incorporated into the circuit board in an unsymmetrical geometry. For example, in crossing one signal line over the other signal lines within the circuit board, the paired conductors often use both circuit board ground planes to accomplish the cross over. In these connector designs, unacceptable levels of high near end cross talk, in the range of 5 to 10 percent, are generated.
It has been discovered that use of extra plated through holes, and in particular unmatched or asymmetrical plated through holes are a significant source of cross talk within the printed circuit board. Moreover, unmatched or asymmetric traces and lines leading to the plated through holes are another source of cross talk.
It has also been discovered that the level of cross talk generated when crossing one signal line of paired conductors across the other signal line pair, off of the circuit board, may be minimized if the positioning of the crossing wire is precisely maintained. Unacceptable levels of cross talk are generated primarily when the position of the crossing lines are not maintained in an optimum position or when the lines deviate from an optimum geometry.
While prior art wire and data connector patents have recognized the problem of cross talk, including U.S. Pat. No. 5,571,035, issued to Ferrill, and assigned to The Whitaker Corporation for a Divergent Load Bar; U.S. Pat. No. 4,601,530 issued to Coldren et al., and assigned to AMP, Inc., for an Electrical Connector And Wire Assembly Method, there are no examples known to the Applicant that recognize and resolve the problem of imprecise crossing of signal lines or the introduction of cross talk in a circuit board due to unmatched and asymmetric plated through holes.
Accordingly, it would be desirable to have a method and apparatus for use with or as a data connector that provides a way to minimize signal wire cross talk by optimally transitioning signal cable wires, off of the circuit board, between industry standard geometries and by minimizing signal cross talk in the connector circuit boards by symmetrical design of the circuit boards. Such improvements and results have not been seen or achieved in the relevant art.